NRC Generic Letter 1983-28
UNITED STATES
L LNUCLEAR REGULATORY COMMISSION
0: WASHINGTON, D. C. 20555 October 7, 1992 TO: ALL LIGHT-WATER REACTOR LICENSEES AND APPLICANTS
SUBJECT: SUPPLEMENT 1 TO GENERIC LETTER 83-28, 'REQUIRED ACTIONS BASED'ON
GENERIC IMPLICATIONS OF SALEM.ATWS.EVENTS
PURPOSE
The U.S. Nuclear Regulatory Commission (NRC) is issuing this generic.letter supplement to inform.licensees that the actions of items.:4i2.3 (life testing)
and 4.2.4 (periodic replacement of breakers or components) as originally described in the enclosure to Generic Letter (GL).83-28, "Required Actions Based on Generic Implications of Salem ATWS Events" are no longer heeded.
BACKGROUND
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On February 22 and 25, 1983, the Salem Nuclear Generating Station experienced anticipated transient without scram (ATWS) events. These'events'.prompted the NRC to issue IE Bulletin 83-01, "Failure of Reactor Trip Breakers (Westinghouse DB-50) to Open on Automatic Trip Signal," to addre'ss'the'short- term corrective actions. The NRC also formed a task.force .to asses.s..the.'
generic implications'of these events. Upon reviewing the findings c6f the task force, the NRC issued GL 83-28.
In GL 83-28, the staff requested the licensees to implement. long.-term corrective actions in response to the Salem events. _GL.83-28 included two1 major actions to improve the reliability of the reactor ttrJip system:
(1)install a plant modification that provided for the automatic.actuation of the shunt trip attachment of the reactor trip breaker (RTB) following any automatic reactor trip signal, and (2)establish a comprehensive program of preventive maintenance and surveillance testing to ensure reliable RTB operation. In addition, items 4.2.3 and 4.2.4 of GL 83-28 requested licensees to perform life testing of RTBs and periodically to replace the breakers or components in accordance with their demonstrated life.
THE STAFF'S REVISED POSITION ON THE LIFE TESTING OF BREAKERS
The modifications to automatically.actuate the shunt trip attachments of RTBs.
following any automatic reactor trip signal and the program of preventive maintenance and surveillance testing requested by GL 83-28 have beeh- implemented by licensees. However, the life testing and program for periodic replacement of breakers or components requested. by items 4.2.3 and .4.2.4 of GL 83-28 have not been fully implemented. In response to these items, many
9210050243 77)3/4e-. 5 GL
Generic Letter 83-28, Supp. 1 -2- October 7, 1992
2 licensees have referenced WCAP-108521 for DB-50 RTBs, WCAP-10835 for DS-416 RTBs, and a joint Combustion Engineering and Babcock and Wilcox trending program for General Electric (GE) AK-2 RTBs. The staff has not found these responses to be acceptable-primarily because no life testing was conducted for the GE RTBs and only limited testing was conducted for the Westinghouse RTBs.
The licensees contend that further life testing of the RTBs is not necessary because of their extensive quality assurance, preventive maintenance, and surveillance testing programs. In the process of determining if additional guidance on items 4.2.3 and 4.2.4 was needed, the staff reviewed operating experience for the period 1986 through early 1991 based upon information in the Nuclear Plant' Reliability Data System and in Licensee Event Reports. The review revealed that the-vast majority of reported failures have been failures to close, rather than failures to open, or degraded conditions detected during planned maintenance, testing, and inspection. Three cases of slow opening were identified, as well as several cases where either the shunt trip or the undervoltage trip attachment, but not both, failed to perform satisfactorily.
However, the review identified only one failure of a RTB to open, in which both the undervoltage and'the shunt trip attachments failed to cause the breaker to open. Sincelthe staff conducted this review in December 1991, there has been an additional'instance in which a RTB failed to fully open on demand during a routine surveillance test. In light of this RTB operating experience, the staff has concluded that the actions already completed pursuant to GL 83-28 have been effective in improving RTB reliability to open and that further actions to address the end-of-life degradation in breaker reliability are not justified. Furthermore, since issuing GL 83-28, the NRC
has promulgatedthe requirements for reducing the risk from ATWS events in
10 CFR 50.2'. The modifications assocF-ate-iT-wth this regulation- further----
reduce the risk resulting from the failure of RTBs. Therefore, the staff concludes that licensee actions in response to items 4.2.3 and 4.2.4 of GL 83-28 are not necessary.
To the extent that licensees may have made commitments to programs for periodically replacing RTBs or components in responses to GL 83-28, they may review and modify these programs taking into account their plant-specific operating experience, maintenance programs, and root cause determination programs for RTBs.'
1WCAP-10852, "Report of the DB-50 Reactor Trip Breaker, Shunt and Undervoltage Trip Attachments, Life Cycle Tests," James P. Chizmar, et al, May 1985
2 WCAP-10835, "Report of the DS-416 Reactor Trip Breaker Undervoltage and Shunt Trip Attachments, Life Cycle Tests," James P. Chizmar, et al, May 1985
AN
Generic Letter 83-28, Supp. 1 -3- October 7, 1992
BACKFIT DISCUSSION
In issuing this generic letter supplement, the staff is relaxing the original positions taken in items 4.2.3 and 4.2.4 of GL 83-28, and hence this generic letter supplement is not considered a backfit. The staff prepared an evaluation of the positions in this generic letter supplement in accordance with the charter of the Committee to Review Generic Requirements (CRGR) and concluded that the public health and safety and common defense and security will be adequately protected, and the proposed changes will not affect the public health and safety. This evaluation is available in the public document room with the minutes of the 220th meeting of the CRGR.
This generic letter supplement does not seek to collect any information, and hence, the Paperwork Reduction Act does not apply.
No response is required to this letter. If you have any questions regarding this matter, please contact the technical contact or the lead project manager listed below. I
Sincerely, James G. Partlow Associate Director for Projects Office of Nuclear Reactor Regulatibh Enclosure:
List of Recently Issued Generic Letters
Technical Contact:
Pi eter C. Wen, NRR
(:301) 504-2832 Lead Project Manager: Leonard N. Olshan, NRR
(301) 504-3018
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Generic Letter 83-28, Supp. 1 -3- October 7, 1992
BACKFIT DISCUSSION
In issuing this generic letter supplement, the staff is relaxing the original positions taken in items 4.2.3 and 4.2.4 of GL 83-28, and hence this generic letter supplement is not considered a backfit. The staff prepared an evaluation of the positions in this generic letter supplement in accordance with the charter of the Committee to Review Generic Requirements (CRGR) and concluded that the public health and safety and common defense and security will be adequately protected, and the proposed changes will not affect the public health and safety. This evaluation is available in the public document room with the minutes of the 220th meeting of the CRGR.
This generic letter supplement does not seek to collect any information, and hence, the Paperwork Reduction Act does not apply.
No response is required to this letter. If you have any questions regarding this matter, please contact the technical contact or the lead project manager listed below.
Sincerely, ORIGINAL SIGNED:
James G. Partlow Associate Director for Projects Office of Nuclear Reactor Regulation Enclosure:
List of Recently Issued Generic Letters
Technical Contact:
Peter C. Wen, NRR
(301) 504-2832 Lead Project Manager: Leonard N. Olshan, NRR
(301) 504-3018 DISTRIBUTION w/enclosure PCWen, NRR
Central Files OGCB R/F
PWen R/F
Document Name: 8328SUP .GL
- SEE PREVI US CONCURRENCESURE
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PCWen ACThadani SLewis TechEd CHBerlinger
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Generic Letter 83-28, Supp. 1 -3- No response is required to this letter. If you have any questions regarding this matter, please contact the technical contact listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
Sincerely, f
James G. Partlow Associate Director for Projects Office of Nuclear Reactor Regulation Enclosure:
List of Recently Issued Generic Letters
Technical Contact:
Peter C. Wen, NRR
(301) 504-2832 DISTRIBUTION w/enclosure PCWen, NRR
Central Files OGCB R/F
PWen R/F
GENERIC LETTER 8328 SUPP 1
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Generic Letter 83-28, Supp. 1 -3- any questions regarding No response is required to this letter. If you have list below.
this matter, please contact the technical contact Sincerely, James G. Partlow Associate Director for Projects Office of Nuclear Reactor Regulation Enclosure:
List of Recently Issued Generic Letters
Technical Contact:
Peter C. Wen, NRR
(301) 504-2832 DISTRIBUTION w/enclosure PCWen, NRR
Central Files OGCB R/F
PWen R/F
GENERIC LETTER 8328 SUPP 1 ADP/NRR ADT/NRR D/DOEA:NRR
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